1. Field of the Invention
The present invention relates to a viscous fluid type heat generator in which a viscous fluid is subjected to a shearing action to generate heat that is in turn transmitted to a circulating heat-transfer or heat-exchange fluid in a heat receiving chamber, and is carried by the heat-transfer fluid to a desired heated area, such as a passenger compartment in an automobile. More particularly, the present invention relates to a viscous fluid type heat generator adapted for being used as a supplementary heat source incorporated in an automobile heating system, provided with a heat generation augmenting means incorporated therein.
2. Description of the Related Art
Japanese Unexamined Patent Publication (Kokai) No. 2-246823 (JP-A-2-246823) discloses a typical automobile heating system in which a viscous fluid type heat generator, to generate heat by using a viscous fluid generating heat when it is subjected to shearing action, is incorporated. The viscous fluid type heat generator disclosed in JP-A-2-246823 includes a pair of mutually opposing front and rear housings tightly secured together by appropriate tightening elements, such as through bolts, to define an inner heat generating chamber and a heat receiving chamber arranged adjacently to the heat generating chamber. The fluid-tight heat generating chamber is formed as a fluid-tight chamber and is isolated from the heat receiving chamber by a partition wall through which the heat is exchanged between the viscous fluid in the fluid-tight heat generating chamber and the water in the heat receiving chamber. The heat exchanging water is introduced into the heat receiving chamber through a water inlet port and delivered from the heat receiving chamber toward an external heating system, and the water is constantly circulated through the heat generator and the external heating system.
A drive shaft is rotatably supported in the front housing via anti-friction bearing so as to support thereon a rotor element in such a manner that the rotor element is rotated with the drive shaft within the fluid-tight heat generating chamber. The rotor element has outer faces which are face-to-face with the inner wall surfaces of the fluid-tight heat generating chamber and form therebetween a small gap in the shape of labyrinth grooves, and a viscous fluid is supplied into the fluid-tight heat generating chamber so as to fill the small gap, i.e., the labyrinth grooves between the rotor element and the wall surfaces of the fluid-tight heat generating chamber.
When the drive shaft of the viscous fluid type heat generator incorporated in the automobile heating system is driven by an automobile engine, the rotor element is also rotated within the fluid-tight heat generating chamber so as to apply a shearing action to the viscous fluid held between the wall surfaces of the fluid-tight heat generating chamber and the outer faces of the rotor element. Thus, the viscous fluid which generally consists of a polymer material, typically a silicone oil having a chain molecular structure presenting a high viscosity, generates heat due to the shearing action applied thereto. The heat is transmitted from the viscous fluid to the heat exchanging water flowing through the heat receiving chamber. The heat exchanging water carries the heat to the heating circuit of the automobile heating system.
In the viscous fluid type heat generator, the amount of heat generation depends on an extent of contact area of the viscous fluid with the outer faces of the rotor element and with the inner wall surfaces of the fluid-tight heat generating chamber. Namely, when the contact area is large, the heat generation by the viscous fluid is energized to supply a large amount of heat.
On the other hand, when a viscous fluid type heat generator is used as a supplementary heat source for an automobile heating system, the heat generator must be as compact as possible so as to permit the heat generator, per se, and all the other various auxiliary equipment of the automobile, to be mounted in a limited mounting area in an engine compartment. To this end, the conventional viscous fluid type heat generator is internally provided with labyrinth grooves formed in the fluid-tight heat generating chamber in order to expand the fluid-tight space defined between the axially opposite end faces of the rotor element and the inner wall surfaces of the housing, and filled with the viscous fluid generating heat during the rotation of the rotor element. Namely, an expansion in the contact area of the viscous fluid with the end faces of the rotor element and the inner wall surfaces of the housing is achieved by the provision of the labyrinth grooves without causing an increase in the entire physical size of the viscous fluid heat generator.
Nevertheless, the provision of the above-mentioned labyrinth in the fluid-tight heat generating chamber is very cumbersome from the point of view of manufacturing technique, and is disadvantage from the point of view of preventing manufacturing cost of the heat generator.
Further, in the conventional viscous fluid type heat generator, the labyrinth provided in the heat generating chamber is arranged so that labyrinth-forming projections formed in the inner wall surfaces of the housing and those formed in the outer faces of the rotor element extend concentrically with one another about the axis of rotation of the rotor element. Therefore, when both labyrinth-forming projections are inaccurately manufactured and assembled, the rotor element might mechanically interfere with the housing when the former is rotated.
Japanese Unexamined (Kokai) Patent publication No. 3-57877 (JP-A-3-57877) discloses a different type of viscous fluid type heat generator in which a rotor element rotated by a drive shaft is housed in a chamber of a rotatable body formed by a pair of confronting cover and housing. A radially outer portion of the rotor element and a confronting portion of the housing are provided with labyrinth-forming projections extending circumferentially to form a fluid-tight labyrinth generally extending in a circumferential direction. A heat generating gap is defined in the fluid-tight labyrinth, and filled with viscous fluid such as silicone oil, to perform heat generation in response to an application of shearing action to the fluid. Namely, the fluid-tight labyrinth is provided as a means for making the heat generating region as large as possible.
The cover is provided with an impeller arranged in a heat receiving chamber so as to provide a resistance against the rotation of the rotatable body. The rotation of the rotor element causes rotation of the rotatable body via the viscous fluid. At this stage, due to provision of the impeller, there occurs a difference in speed between the rotation of the rotor element and that of the rotatable body, and therefore, heat is generated by the viscous fluid held in the heat generating gap in the fluid-tight labyrinth.
Although the rotor element of JP-A-3-57877 is provided with one or a plurality of through-holes formed in a radially inner portion thereof, these through-holes do not increase an amount of generation of heat by the viscous fluid. This is because the viscous fluid is mainly filled in the above-mentioned annular heat generating gap in the fluid-tight labyrinth region, and is not filled in the region located adjacent to the through-holes. Therefore, the through-holes do not act so as to increase the strength of the shearing action applied to the viscous fluid, and should be considered as passageway means for providing a fluid communication between both sides of the rotor element, and for permitting the viscous fluid to pass therethrough as required.